buffer lets you split a list into smaller max-size ones

2 files changed, 94 insertions, 0 deletions

diff --git a/main/src/cgeo/geocaching/utils/MiscUtils.java b/main/src/cgeo/geocaching/utils/MiscUtils.java
new file mode 100644
index 0000000..122c4eb
--- /dev/null
+++ b/main/src/cgeo/geocaching/utils/MiscUtils.java
@@ -0,0 +1,40 @@
+package cgeo.geocaching.utils;
+
+import org.apache.commons.collections4.iterators.IteratorIterable;
+import org.apache.commons.lang3.NotImplementedException;
+
+import java.util.Iterator;
+import java.util.List;
+
+final public class MiscUtils {
+
+    private MiscUtils() {}  // Do not instantiate
+
+    public static <T> Iterable<List<T>> buffer(final List<T> original, final int n) {
+        if (n <= 0) {
+            throw new IllegalArgumentException("buffer size must be positive");
+        }
+        return new IteratorIterable<List<T>>(new Iterator<List<T>>() {
+            final int size = original.size();
+            int next = 0;
+
+            @Override
+            public boolean hasNext() {
+                return next < size;
+            }
+
+            @Override
+            public List<T> next() {
+                final List<T> result = original.subList(next, Math.min(next + n, size));
+                next += n;
+                return result;
+            }
+
+            @Override
+            public void remove() {
+                throw new NotImplementedException("remove");
+            }
+        });
+    }
+
+}
diff --git a/tests/src/cgeo/geocaching/utils/MiscUtilsTest.java b/tests/src/cgeo/geocaching/utils/MiscUtilsTest.java
new file mode 100644
index 0000000..2ee99c4
--- /dev/null
+++ b/tests/src/cgeo/geocaching/utils/MiscUtilsTest.java
@@ -0,0 +1,54 @@
+package cgeo.geocaching.utils;
+
+import junit.framework.TestCase;
+
+import java.util.LinkedList;
+import java.util.List;
+
+public class MiscUtilsTest extends TestCase {
+
+    public static void testBufferEmpty() {
+        for (final List<String> s: MiscUtils.buffer(new LinkedList<String>(), 10)) {
+            fail("empty collection should not iterate");
+        }
+    }
+
+    public static void testMultiple() {
+        final List<Integer> list = new LinkedList<Integer>();
+        for (int i = 0; i < 50; i++) {
+            list.add(i);
+        }
+        int count = 0;
+        for (final List<Integer> subList: MiscUtils.buffer(list, 10)) {
+            assertEquals("each sublist has the right size", 10, subList.size());
+            assertEquals("sublist has the right content", count * 10, (int) subList.get(0));
+            count++;
+        }
+        assertEquals("there are the right number of sublists", 5, count);
+    }
+
+    public static void testNonMultiple() {
+        final List<Integer> list = new LinkedList<Integer>();
+        for (int i = 0; i < 48; i++) {
+            list.add(i);
+        }
+        int count = 0;
+        for (final List<Integer> subList: MiscUtils.buffer(list, 10)) {
+            assertTrue("each sublist has no more than the allowed number of arguments", subList.size() <= 10);
+            count += subList.size();
+        }
+        assertEquals("all the elements were seen", 48, count);
+    }
+
+    public static void testArguments() {
+        try {
+            MiscUtils.buffer(new LinkedList<Integer>(), 0);
+            fail("an exception should be raised");
+        } catch (final IllegalArgumentException e) {
+            // Ok
+        } catch (final Exception e) {
+            fail("bad exception raised: " + e);
+        }
+    }
+
+}